Design, analysis and application of flux-modulated machines

Abstract

Electric machines have a history of nearly 200 years. They have played a key role in the electrification of our society and they are widely used nowadays both in industry and our everyday life. A basic rule for designing an electric machine is that the pole number of the stator and the pole number of the rotor should be equal. However, the emergence of flux-modulated (FM) machines breaks this rule. In a FM machine, the excitation field and the armature field interact over their harmonic components, which is the so-called flux modulation effect or magnetic gearing effect since it was first used in magnetic gears. Due to their special working principle, the FM machines own some different characteristics from conventional electric machines such as more flexible pole number combination and the possibility of realizing multi-port design. These features of FM machines make them suitable for a number of certain applications. In this thesis, the design, analysis, and the potential applications of FM machines are introduced. The thesis mainly includes the following contents. a) A literature review on the development of different types of FM machines is presented. These machines include the basic FM machines (BFMMs), the vernier permanent-magnet (PM) machines (VPMMs), the doubly-fed reluctance machines (DFRMs), and the dual-excitation PM machines (DEPMMs). b) The magnetics gears and the flux modulation effect are introduced. A unified theory for FM machines is proposed. Using the proposed theory, the operating principles of different FM machines are explained in a unified way. c) The general design rules for different components, namely the winding, the PM and the flux modulation poles, in a FM machine are introduced. d) A quantitative performance comparison among different types of FM machines is conducted. Based on the comparison result, the potential applications of these machines are identified. e) Two FM machines are designed for electric vehicle propulsion and wind power generation, respectively, to showcase the potential applications of FM machines. The performance of these two machines are analyzed using FEM. Prototypes are made and tested for validation.